The invention relates to a method and a device for position-exact and dimension-exact chamfering of a clamped pipe end with respect to the outer or inner diameter of the pipe, especially for producing a welding chamfer, which must be applied, in general, with great precision with respect to the inner surface of the pipe, in order to be able to produce a welding connection between abutting pipe ends with respect to all specifications. The manufacture of such a welding chamfer is problematic because a considerable deviation from roundness as well as wall thickness variations due to radial displacement of the inner diameter relative to the outer diameter may occur in seamless pipes. Even though welded pipes have no great wall thickness variation, these pipes may have a greatly oval contour and, in the area of the welding seam, may exhibit bulges at the interior and/or exterior. Furthermore, for seamless and welded pipes a diameter deviation is generally acceptable which, however, does not ensure an exact welding seam preparation without taking into consideration the actual inner or outer diameter of the pipe.
The deviation from roundness of the pipe can be compensated according to U.S. Pat. No. 3,724,303, in which a device for combined cutting and chamfering of pipe ends is disclosed, by arranging the chamfering tool on a workpiece holder which is elastically supported via a roller or a ball on the outer surface of the pipe. In this manner, an outer chamfer as well as an inner chamfer can be applied position-exact and dimension-exact relative to the outer circumference of the pipe. When it is desired to apply an outer and/or inner chamfer position-exact and dimension-exact relative to the inner surface of the pipe, the tool holder must be supported in a similar manner at the inner surface of the pipe. This known device thus operates according to the tracing method with a mechanical sensing device which is directly operatively coupled with the chamfering device.
This known device is disadvantageous because the machining process of chamfering is not dividable into a fast rough-machining process and a slower finish-machining process so that the advance for the entire machining process must be based on the required surface quality to be produced with the finish-machining process. Accordingly, the machining time is unnecessarily long because only a small cutting output is achievable. Furthermore, an irregular surface of the chamfer will result when the tracing device runs across cuttings or a welding seam bulge which negatively affects the quality of the chamfer to be produced.
It is an object of the invention to provide a method and device with which a pipe end can be chamfered position-exact and dimensionexact with respect to the outer or inner diameter of the pipe and with which the chamfer remains unaffected by a deviation from roundness, by wall thickness deviations, cuttings or welding seam bulges.